Changeset 29768

[toolchain] invoke patch-specs.sh in the gcc/final install stage.
Patch up OpenWrts own cross toolchains to always search headers
and libraries in $STAGING_DIR, this should solve most issues with
missing headers, indirect linking and not found libraries.
At a later stage, all -I and -L flags will be purged from
TARGET_LDFLAGS and TARGET_CPPFLAGS.